In particular, turning off the UNC paths transformation might be seen as a
​security measure.
Here, the "file:" links are user-oriented and can't be embedded in a <img>
or Javascript code, I don't really see what could be the risk, so I think
it's OK to enable this feature.
Firefox users can use the ​LocalLink plugin
(​install).
Of course, if someone can demonstrate that this feature presents
a security risk, I'll disable it by default in future releases.